I have made a couple attempts at setting up this problem, but both have failed miserably so far. So some help setting it up will be appreciated.For a certain model of car the distancedrequired to stop the vehicle if it is traveling atvmi/h is given by the formula

$\displaystyle d = v + \frac{v^2}{20}$

wheredis measured in feet. Kerry wants her stopping distance not to exceed 240 ft. At what range of speeds can she travel?

Also, since I am having so much trouble with application problems, is there any tips you guys can give me on how I should attack future math problems such as these? Thanks.